رفع خطای The DELETE / INSERT statement conflicted with the FOREIGN KEY constraint

Msg 547, Level 16, State 0
The DELETE statement conflicted with the REFERENCE constraint "FK_Enrollment_Student".
The conflict occurred in database "SchoolDB", table "dbo.Enrollment", column 'StudentId'.

Msg 547, Level 16, State 0
The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Enrollment_Course".
The conflict occurred in database "SchoolDB", table "dbo.Course", column 'CourseId'.

DELETE FROM Student WHERE StudentId = 5;   -- خطا: Enrollment فرزند دارد

SELECT * FROM Enrollment WHERE StudentId = 5;

BEGIN TRANSACTION;
  DELETE FROM Enrollment WHERE StudentId = 5;
  DELETE FROM Student    WHERE StudentId = 5;
COMMIT;

ALTER TABLE Enrollment DROP CONSTRAINT FK_Enrollment_Student;

ALTER TABLE Enrollment
ADD CONSTRAINT FK_Enrollment_Student FOREIGN KEY (StudentId)
    REFERENCES Student(StudentId) ON DELETE CASCADE;

ALTER TABLE Student ADD IsDeleted BIT NOT NULL DEFAULT 0;
UPDATE Student SET IsDeleted = 1 WHERE StudentId = 5;

INSERT INTO Enrollment (StudentId, CourseId) VALUES (1, 99);   -- CourseId=99 وجود ندارد

SELECT * FROM Course WHERE CourseId = 99;      -- خالی؟ پس درج مجاز نیست

SELECT fk.name AS ForeignKey,
       OBJECT_NAME(fk.parent_object_id)     AS ChildTable,
       OBJECT_NAME(fk.referenced_object_id) AS ParentTable,
       fk.delete_referential_action_desc    AS OnDelete
FROM sys.foreign_keys fk
WHERE fk.referenced_object_id = OBJECT_ID('dbo.Student');

SELECT e.*
FROM Enrollment e
LEFT JOIN Student s ON s.StudentId = e.StudentId
WHERE s.StudentId IS NULL;

ALTER TABLE Enrollment NOCHECK CONSTRAINT FK_Enrollment_Student;
-- ... بارگذاری داده ...
ALTER TABLE Enrollment WITH CHECK CHECK CONSTRAINT FK_Enrollment_Student;  -- بررسی مجدد